The invention relates, generally, to a workpiece holder and, more particularly, to a workpiece holder for use with a machine tool for cutting, boring or drilling workpieces.
The typical machine tool includes a horizontal machine table disposed adjacent to the tool for supporting the workpiece. The table supports a mechanism for gripping the workpiece in a predetermined position relative to the tool.
One such prior art gripping mechanism consists of a pair of jaws supported by the horizontal machine table. The jaws are movably mounted on the table to accommodate workpieces of various sizes and to properly position the workpieces relative to the milling tool. One of the jaws is a "fixed" jaw which, after being initially positioned on the table for a specific workpiece and operation, is not moved. The other jaw is a "movable" jaw having a base mounted to the table and a jaw member slidably supported on the base. The jaw member can be moved relative to the base to releasably grip the workpiece between it and the "fixed" jaw. In the known devices, the jaw member is moved into and out of engagement with the workpiece either by a screw or a camming mechanism.
One problem with the known devices is that neither the screw nor the camming mechanism can accurately and precisely position new workpieces during repetitive machine operations. As a result, numerous man hours are lost precisely positioning each new workpiece. Moreover, the known devices require relatively extensive manipulations of either the screw or camming member to grip, release and position the workpiece.
One known alternative to the jaw-type devices discussed above, are straps which extend over the top of the workpiece to, in effect, tie the workpiece to the table. The straps, however, cannot precisely position workpieces during repetitive machine operations. Moreover, because these straps overlie the workpiece, access to the workpiece by the machine tool is partially obstructed.
A workpiece holder that ca simply and precisely grip and position workpieces for repetitive machine operations is desired.